Outline

1. Outline • Introduction to Ecology • Evolution and Natural Selection • Physiological Ecology • Behavioural Ecology

2. Behavioural Ecology

3. Behavioural Ecology • The study of ecological and evolutionary processes that explain the occurrence and adaptive function of behaviour • Examples of potential questions: • Why do birds migrate? • Why do grazing animals condense into herds?

4. Behaviour • Affects an individual’s ability to survive and reproduce in a particular environment • Develops under the influence of both genetic inheritance and environmental experience (learning) • the genetic component of behaviour is subject to natural selection

5. Behaviour to maintain internal conditions

6. Behaviour to get food or prevent becoming food

7. Behaviour to reproduce

8. Plants manipulate behaviour

9. Outline • Reproduction: Why have sex? • Life histories and mate choice • Predation: • Optimal foraging • Applications to fisheries management

10. Outline • Reproduction: Why have sex? • Life histories and mate choice • Predation: • Optimal foraging • Applications to fisheries management

11. Why have sex? Ch. 7.1-7.2, Bush

12. Outline • The basics of sex • The evolution of sex • Variations in sexual systems

13. Outline • The basics of sex • The evolution of sex • Variations in sexual systems

14. Reproduction • The goal of reproduction, for any organism, is to ensure the survival of its genetic lineage Two ways to do this: • ASEXUAL: offspring are exact (almost) genetic copies of a single parent • SEXUAL: chromosomes of two parents are segregated and recombined so that no two offspring are identical to each other or to either parent

15. Most organisms are sexual • Of the 1.8 million known species only 2000 of them are totally asexual

16. Asexuality is concentrated among the basal organisms

17. Asexual reproduction • The cell divides to produce two daughter cells • This type of reproduction can be very rapid; several generations can be produced each hour

18. Sex = meiosis • Meiosis is the process whereby gametes are made with half the number of chromosomes • The original number of chromosome is reformed when two gametes come together

19. Meiosis versus mitosis

20. Outline • The basics of sex • The evolution of sex • Variations in sexual systems

21. Why did sex evolve? • Life originated without sex (as best we can tell) so sexual reproduction is something that had to evolve • There are a large number of disadvantages to sexual reproduction which makes the evolution of sex a conundrum

22. Sex is not necessary for all life • Some plants and animals have entirely abandoned sex • Others have sex only when its convenient and are asexual most of the time (facultatively sexual)

23. Sex in the news…

24. Ancient asexuals: Bdelloid rotifers • bdelloid rotifers date back ~100 million years • Despite bdelloids' asexuality, they've diversified into 380 species

25. Facultative sexuality in animals • In some animals, such as Hydra, asexual reproduction can occur through budding • These animals are still capable of reproducing sexually as well • Sexual and asexual processes are governed by environmental conditions

26. Parthenogenesis – offspring from unfertilized eggs Cnemidophorus velox, a parthenogenic lizard

27. Aphids – asexual and sexual • Females give birth to live females during the summer months • As winter approaches, both males and females are produced, which mate to produce eggs

28. The Cost of Sex • The cost of males • The cost of recombination • The cost of mating

29. The Cost of Males

30. Passing on genes is like tossing coins • Two copies exist for each gene • Whether you pass on a certain copy of a gene is an independent event for each child • If you have two children, sometimes you will pass on the same copy to both children (leaving the second copy passed on to neither child)

31. Fitness FITNESS: • the number of offspring an individual produces that survive to reproduce themselves • Fitness = 1.0 means that individuals of this phenotype are successfully passing on 100% of their genes, on average

32. How is fitness calculated • Fitness = the number of genes passed on to the next generation • Because diploid organisms (I.e., most organisms) only pass on half of their genes to each child, they must have two offspring living to reproductive age to have Fitness = 1 • Fitness = 1 does not exactly mean that you have passed on 100% of your genes to the next generation (Remember: sometimes you send two copies of the same gene and zero copies of the other)

33. Cost of recombination Asexual Sexual F F F F F F M M Fitness 2 1 of females

34. The Cost of Mating • Cost of sexual mechanisms • Chemical attractants • Sexual organs • Flowers • Cost of mating behaviour • Courtship is costly • Potential exposure to predators • Injury • Disease Transmission

35. Sexual Mechanisms

36. Mating Behaviour

37. Injury to females - unintentional • When males are much bigger than females, the females can be injured by intercourse

38. Injury to females - intentional! Callosobruchus maculatus Male genitalia

39. Why hurt the female? • Reducing the fitness of your mate ought to reduce the fitness of yourself as well • Copulation is not always a cooperative venture between the sexes. • In C. maculatus, females mate repeatedly • genital wounding could increase the fitness of male C. maculatus if: • it causes females to postpone remating (less sperm competition) • increase immediate oviposition (egg-laying) rates because females perceive damage as a threat to survival and invest more in current reproduction

40. Costs of mating are widespread • Female Drosophila melanogaster that mate more often die more often • seminal fluid increases female death rate • Fluid is also responsible: • in elevating the rate of female egg in elevating the rate of female egg-laying, • in reducing female receptivity to further matings • in removing or destroying sperm of previous mates

41. Birds, bees, and STD’s • Most organisms are plagued by a few sexually-transmitted diseases • E.g., earwigs, frogs, koalas, or humans • Ustilago violacea (smut fungus) infects flowers of Silene alba and is transferred via pollinators

42. Sexuality must have its advantages • Hardly any asexual lineages seem old, and fossil evidence has suggested that asexuality is a dead end • The prevalence of sexuality amongst species is caused not because asexual species don't evolve, but because they don't last

43. Sex increases variation

44. Sex increases variation • Genes from maternal and paternal parent get “shuffled up” when gametes are made • Causes some gametes to have “superfit” genotypes and others to have “superunfit” genotypes

45. Sex leads to more variation in offspring

46. Sex and speed of evolution • More variation leads to natural selection operating faster • Most selection, however, is stabilizing selection, as individuals are well-adapted for a given environment and try to stay that way

47. Sex and speed of evolution • What aspect of the environment is so variable that the production of variable offspring could offset the cost of sex? - Parasites and pathogens • Hosts are constantly evolving to protect themselves from parasites and parasites are constantly evolving to overcome their host’s defenses • Parasites and hosts are locked in a host-parasite arms race

48. Red Queen Hypothesis "Well in our country," said Alice, still panting a little. "you'd generally get to somewhere else-if you ran very fast for a longtime as we’ve been doing.” "A slow sort of county!" said the Queen. "Now, here, you see, it takes all the running you can do to keep in the same place."

49. Evidence for Red Queen Hypothesis • In top minnows, sexual and asexual lineages coexist • Sexual lineages are the least susceptible to parasites • Genetic variation needed to keep up with evolution of parasites

50. Muller’s Ratchet • Vast majority of mutations are detrimental • Mutation acquisition is a one-way process in the genomes of asexuals • In Salmonella typhimurium 444 lineages started from a single colony • After 1700 generations, 1% of lineages showed decrease in fitness (growth rate) but no lineages showed increased fitness